GSSCredentialSelector.m   [plain text]

/*
* Copyright (c) 2011 Kungliga Tekniska Högskolan
* (Royal Institute of Technology, Stockholm, Sweden).
* All rights reserved.
*
* Portions Copyright (c) 2011 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

#import <stdio.h>

#import <Foundation/Foundation.h>
#import <Heimdal/krb5.h>
#import <GSS/gssapi_spi.h>
#import <GSS/gssapi_plugin.h>

#include <syslog.h>
#include <assert.h>

/**
* Icky code that prints the target name and replace the cred with another cred that hard coded in the module
*/

#define GSSC_MAGIC 0x47111147

struct gsssel_ctx {
int magic;
};

static const char selectuser[] = "lha@KTH.SE";
static const char *replacenames[] = {
"host@svn.h5l.org",
NULL
};

static gss_cred_id_t
isc_replace_cred(gss_name_t target, gss_OID mech, gss_cred_id_t original_cred, OM_uint32 flags)
{
OM_uint32 maj_stat, min_stat;
gss_buffer_desc buffer;
gss_name_t name;
gss_cred_id_t newcred;
bool exchange = false;
size_t n;

/*
* Using gss_display_name() is wrong, however it the best we can
* do right now.
*
* We should use gss_import_name() and then compare the name with
* gss_compare_name(), the only issue with that is that comparing
* names fragile and do not work as expected wrt to case of
* string, and in case or Kerberos, hostbased service gets
* affected by realm.
*/

maj_stat = gss_display_name(&min_stat, target, &buffer, NULL);
if (maj_stat == GSS_S_COMPLETE) {
syslog(LOG_ERR, "ISC-replace-cred target name: %.*s", (int)buffer.length, (char *)buffer.value);
for (n = 0; replacenames[n]; n++) {
if (memmem(buffer.value, buffer.length, replacenames[n], strlen(replacenames[n])) != NULL)
exchange = true;
}
gss_release_buffer(&min_stat, &buffer);
}
if (!exchange) {
syslog(LOG_ERR, "ISC-replace-cred not replacing");
return NULL;
}

buffer.value = (char *)(uintptr_t)selectuser;
buffer.length = strlen(selectuser);
maj_stat = gss_import_name(&min_stat, &buffer, GSS_C_NT_USER_NAME, &name);
if (maj_stat != GSS_S_COMPLETE)
return NULL;

maj_stat = gss_acquire_cred(&min_stat, name, GSS_C_INDEFINITE, GSS_C_NO_OID_SET, GSS_C_INITIATE,
&newcred, NULL, NULL);
gss_release_name(&min_stat, &name);
if (maj_stat != GSS_S_COMPLETE)
return NULL;

syslog(LOG_ERR, "ISC-replace-cred replacing cred to: %s", selectuser);

return newcred;
}

static krb5_error_code
gsssel_init(krb5_context context, void **ptr)
{
struct gsssel_ctx *ctx = calloc(1, sizeof(*ctx));

if (ctx == NULL)
return ENOMEM;

ctx->magic = GSSC_MAGIC;

*ptr = ctx;
return 0;
}

static void
gsssel_fini(void *ptr)
{
struct gsssel_ctx *ctx = ptr;

assert(ctx->magic == GSSC_MAGIC);

free(ctx);
}

gssapi_plugin_ftable gssapi_plugin = {
GSSAPI_PLUGIN_VERSION_1,
gsssel_init,
gsssel_fini,
"gssapi credential selector",
0,
isc_replace_cred
};